In the processing or treatment of flue gas or gas streams, dry flue gas desulfurization (DFGD) systems are known. In DFGD system processes, lime (CaO) is first converted to hydrated lime (Ca(OH)2) before contact with the flue gas. The hydrated lime contacts the flue gas as a dry or moistened powder in a circulating dry scrubber (CDS) DFGD system. An example of such a CDS DFGD system is the ALSTOM NID™ system (ALSTOM Power Inc., Paris, France) (NID).
U.S. Pat. No. 4,610,849, invented by John Van Camp et al., discloses a spray dryer absorber (SDA) DFGD system that uses an aqueous slurry containing an alkaline reagent for reaction with sulfur oxides in a flue gas. This SDA DFGD system uses an array of spaced apart nozzles adapted to introduce a plurality of spray patterns into a reaction zone. The spaced apart nozzles introduce the aqueous slurry containing an alkaline reagent into the reaction zone for contact with the flue gas for reaction of the alkaline reagent and the sulfur oxides in the flue gas.
WO 97/37747, invented by Stefan Ahman et al., discloses a device for a CDS DFGD system useful for discharging and distributing an absorbent material in a flue gas duct. Accordingly, in a vertical flue gas duct for flue gases containing gaseous pollutants, a discharging and distributing device is arranged to discharge and distribute a particulate absorbent material reactive with the gaseous pollutants in the flue gas to convert the gaseous pollutants to a separable dust.
While methods and equipment capable of removing both particulate and gaseous pollutants from a flue gas stream exist, there remains a need for improved DFGD methods and equipment that also protect associated system air preheaters from pollutant corrosion while maintaining efficiency and effectiveness.